The appropriate way to stop systemd via a signal is to use SIGRTMIN+3 (or, I think, SIGRTMIN+4). The lxc-stop binary automatically determines whether the container will respond to this signal and handles it appropriately. Therefore, we should use that binary with ExecStop instead of using a signal (in the service file).

On Wed, May 31, 2017 at 07:10:01PM -0400, JD Friedrikson wrote:
> Debian's packaged version of LXC currently is not able to stop systemd-based containers as they have not responded to SIGPWR as of https://github.com/lxc/lxc/commit/8eb62c245e9b67b451ba0766f3ecd7c6f2081d73 .
>
> The appropriate way to stop systemd via a signal is to use SIGRTMIN+3 (or, I think, SIGRTMIN+4). The lxc-stop binary automatically determines whether the container will respond to this signal and handles it appropriately. Therefore, we should use that binary with ExecStop instead of using a signal (in the service file).